/*
 * Copyright 2012-2017 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.boot.autoconfigure;

import java.lang.annotation.Annotation;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.HashSet;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;

import org.springframework.boot.context.annotation.DeterminableImports;
import org.springframework.core.annotation.AnnotatedElementUtils;
import org.springframework.core.annotation.AnnotationAttributes;
import org.springframework.core.annotation.AnnotationUtils;
import org.springframework.core.io.support.SpringFactoriesLoader;
import org.springframework.core.type.AnnotationMetadata;
import org.springframework.util.ClassUtils;
import org.springframework.util.LinkedMultiValueMap;
import org.springframework.util.MultiValueMap;
import org.springframework.util.ObjectUtils;

/**
 * Variant of {@link EnableAutoConfigurationImportSelector} for
 * {@link ImportAutoConfiguration}.
 *
 * @author Phillip Webb
 * @author Andy Wilkinson
 */
class ImportAutoConfigurationImportSelector extends AutoConfigurationImportSelector implements DeterminableImports
{

    private static final Set<String> ANNOTATION_NAMES;

    static
    {
        Set<String> names = new LinkedHashSet<String>();
        names.add(ImportAutoConfiguration.class.getName());
        names.add("org.springframework.boot.autoconfigure.test.ImportAutoConfiguration");
        ANNOTATION_NAMES = Collections.unmodifiableSet(names);
    }

    @Override
    public Set<Object> determineImports(AnnotationMetadata metadata)
    {
        Set<String> result = new LinkedHashSet<String>(getCandidateConfigurations(metadata, null));
        result.removeAll(getExclusions(metadata, null));
        return Collections.<Object>unmodifiableSet(result);
    }

    @Override
    protected AnnotationAttributes getAttributes(AnnotationMetadata metadata)
    {
        return null;
    }

    @Override
    protected List<String> getCandidateConfigurations(AnnotationMetadata metadata, AnnotationAttributes attributes)
    {
        List<String> candidates = new ArrayList<String>();
        Map<Class<?>, List<Annotation>> annotations = getAnnotations(metadata);
        for (Map.Entry<Class<?>, List<Annotation>> entry : annotations.entrySet())
        {
            collectCandidateConfigurations(entry.getKey(), entry.getValue(), candidates);
        }
        return candidates;
    }

    private void collectCandidateConfigurations(Class<?> source, List<Annotation> annotations, List<String> candidates)
    {
        for (Annotation annotation : annotations)
        {
            candidates.addAll(getConfigurationsForAnnotation(source, annotation));
        }
    }

    private Collection<String> getConfigurationsForAnnotation(Class<?> source, Annotation annotation)
    {
        String[] classes = (String[]) AnnotationUtils.getAnnotationAttributes(annotation, true).get("classes");
        if (classes.length > 0)
        {
            return Arrays.asList(classes);
        }
        return loadFactoryNames(source);
    }

    protected Collection<String> loadFactoryNames(Class<?> source)
    {
        return SpringFactoriesLoader.loadFactoryNames(source, getClass().getClassLoader());
    }

    @Override
    protected Set<String> getExclusions(AnnotationMetadata metadata, AnnotationAttributes attributes)
    {
        Set<String> exclusions = new LinkedHashSet<String>();
        Class<?> source = ClassUtils.resolveClassName(metadata.getClassName(), null);
        for (String annotationName : ANNOTATION_NAMES)
        {
            AnnotationAttributes merged = AnnotatedElementUtils.getMergedAnnotationAttributes(source, annotationName);
            Class<?>[] exclude = (merged == null ? null : merged.getClassArray("exclude"));
            if (exclude != null)
            {
                for (Class<?> excludeClass : exclude)
                {
                    exclusions.add(excludeClass.getName());
                }
            }
        }
        for (List<Annotation> annotations : getAnnotations(metadata).values())
        {
            for (Annotation annotation : annotations)
            {
                String[] exclude = (String[]) AnnotationUtils.getAnnotationAttributes(annotation, true).get("exclude");
                if (!ObjectUtils.isEmpty(exclude))
                {
                    exclusions.addAll(Arrays.asList(exclude));
                }
            }
        }
        return exclusions;
    }

    protected final Map<Class<?>, List<Annotation>> getAnnotations(AnnotationMetadata metadata)
    {
        MultiValueMap<Class<?>, Annotation> annotations = new LinkedMultiValueMap<Class<?>, Annotation>();
        Class<?> source = ClassUtils.resolveClassName(metadata.getClassName(), null);
        collectAnnotations(source, annotations, new HashSet<Class<?>>());
        return Collections.unmodifiableMap(annotations);
    }

    private void collectAnnotations(Class<?> source, MultiValueMap<Class<?>, Annotation> annotations,
                                    HashSet<Class<?>> seen)
    {
        if (source != null && seen.add(source))
        {
            for (Annotation annotation : source.getDeclaredAnnotations())
            {
                if (!AnnotationUtils.isInJavaLangAnnotationPackage(annotation))
                {
                    if (ANNOTATION_NAMES.contains(annotation.annotationType().getName()))
                    {
                        annotations.add(source, annotation);
                    }
                    collectAnnotations(annotation.annotationType(), annotations, seen);
                }
            }
            collectAnnotations(source.getSuperclass(), annotations, seen);
        }
    }

    @Override
    public int getOrder()
    {
        return super.getOrder() - 1;
    }

    @Override
    protected void handleInvalidExcludes(List<String> invalidExcludes)
    {
        // Ignore for test
    }

}
